Persephone "Penny" Valentine is a former Foundation House Officer at Holby City Hospital, and is the sister to Oliver Valentine.

Time at Holby City Hospital

Penny arrives at Holby General as a Foundation House Officer 1, alongside her brother Oliver. Registrar Jac Naylor takes an instant dislike to her, and ignores her request to work on the hospital's Acute Assessment Unit, placing her instead on the general surgery ward, Keller. After making a good impression on cardiothoracic consultant Connie Beauchamp, Penny is transferred to the cardiothoracic surgery ward, Darwin, where she is mentored by consultant surgeon Elliot Hope. Penny develops feelings for Scott James, a patient awaiting a heart transplant, and the two begin a relationship. During an unrelated case, Penny convinces a reluctant husband to donate his deceased wife's organs, unaware that Scott will be the recipient of her heart. When Elliot discovers their relationship and the link between cases, he holds Penny back a surgical rotation and forbids her to see Scott again. Scott announces his intention to move to Spain, and asks Penny to leave with him. Disillusioned with medicine, Penny agrees; however, Oliver convinces Scott that Penny will come to regret abandoning her career, and Scott rescinds his offer, leaving alone.

When Oliver makes a surgical mistake, he attempts to persuade Penny to take the blame for him. He alters the affected patient's records to substitute his name for Penny's, but is caught by registrar Antoine Malick. Penny is furious - more so when Oliver confesses that he failed his final medical exam and switched his paper with hers. She takes annual leave, and tells Oliver to admit that he is not a qualified doctor to clinical lead Michael Spence, or she will. Upon returning from leave, Penny is called to the scene of a major train accident. She attempts to save a passenger from beneath a carriage, but it collapses on top of her, killing her instantly. After identifying Penny's body, Oliver confesses his cheating to Malick. Malick stops him from telling Hanssen, stating that Oliver is a good doctor and that he will overlook his confession.